NAME

	arch – architecture–specific information and control

SYNOPSIS

	bind –a #P /dev /dev/cputype /dev/ioalloc /dev/iob /dev/iol /dev/iow /dev/irqalloc

DESCRIPTION

This device presents textual information about PC hardware and allows user–level control of the I/O ports on x86–class and DEC Alpha machines. Reads from cputype recover the processor type and clock rate. Reads from ioalloc return I/O ranges used by each device, one line per range. Each line contains three fields separated by white space: first address in hexadecimal, last address, name of device. Reads from irqalloc return the enabled interrupts, one line per interrupt. Each line contains three fields separated by white space: the trap number, the IRQ it is assigned to, and the name of the device using it. Reads and writes to iob, iow, and iol cause 8–bit wide, 16–bit wide, and 32–bit wide requests to I/O ports. The port accessed is determined by the byte offset of the file descriptor.

EXAMPLE

	The following code reads from an x86 byte I/O port. uchar inportb(long port) { uchar data; if(iobfd == –1) iobfd = open("#P/iob", ORDWR); seek(iobfd, port, 0); if(read(iobfd, &data, sizeof(data)) != sizeof(data)) sysfatal("inportb(0x%4.4x): %r\n", port); return data; }

SOURCE

	/sys/src/9/pc/devarch.c

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